
package com.probiz.estore.core.taglib;

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.TagSupport;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.probiz.estore.Constants;

/**
 * <p>
 * This class is designed to put all the public variables in a class to a
 * specified scope - designed for exposing a Constants class to Tag Libraries.
 * </p>
 * 
 * <p>
 * It is designed to be used as follows:
 * 
 * <pre>
 * &lt;tag:constants /&gt;
 * </pre>
 * 
 * </p>
 * 
 * <p>
 * Optional values are "className" (fully qualified) and "scope".
 * </p>
 * 
 * <p>
 * <a href="BaseAction.java.html"><i>View Source</i></a>
 * </p>
 * 
 * @author <a href="mailto:matt@raibledesigns.com">Matt Raible</a>
 * @version $Revision: 1.1 $ $Date: 2006/04/21 02:01:43 $
 * 
 * @jsp.tag name="constants" bodycontent="empty"
 *          tei-class="com.probiz.estore.webapp.taglib.ConstantsTei"
 */
public class ConstantsTag extends TagSupport {
	/**
	 * Maps lowercase JSP scope names to their PageContext integer constant
	 * values.
	 */
	private static final Map	scopes				= new HashMap();
	private static final long	serialVersionUID	= 3258417209566116146L;

	/**
	 * Initialize the scope names map and the encode variable with the Java 1.4
	 * method if available.
	 */
	static {
		scopes.put("page", Integer.valueOf(PageContext.PAGE_SCOPE));
		scopes.put("request", Integer.valueOf(PageContext.REQUEST_SCOPE));
		scopes.put("session", Integer.valueOf(PageContext.SESSION_SCOPE));
		scopes.put("application", Integer.valueOf(PageContext.APPLICATION_SCOPE));
	}

	/**
	 * The class to expose the variables from.
	 */
	public String				clazz				= Constants.class.getName();

	private final Log			log					= LogFactory
															.getLog(ConstantsTag.class);

	/**
	 * The scope to be put the variable in.
	 */
	protected String			scope				= null;

	/**
	 * The single variable to expose.
	 */
	protected String			var					= null;

	public int doStartTag() throws JspException {
		// Using reflection, get the available field names in the class
		Class c = null;
		int toScope = PageContext.PAGE_SCOPE;

		if (scope != null) {
			toScope = getScope(scope);
		}

		try {
			c = Class.forName(clazz);
		} catch (ClassNotFoundException cnf) {
			log.error("ClassNotFound - maybe a typo?");
			throw new JspException(cnf.getMessage());
		}

		try {
			// if var is null, expose all variables
			if (var == null) {
				Field[] fields = c.getDeclaredFields();

				AccessibleObject.setAccessible(fields, true);

				for (int i = 0; i < fields.length; i++) {
					/*
					 * if (log.isDebugEnabled()) { log.debug("putting '" +
					 * fields[i].getName() + "=" + fields[i].get(this) + "' into " +
					 * scope + " scope"); }
					 */
					pageContext.setAttribute(fields[i].getName(), fields[i]
							.get(this), toScope);
				}
			} else {
				try {
					String value = (String) c.getField(var).get(this);
					pageContext.setAttribute(c.getField(var).getName(), value,
							toScope);
				} catch (NoSuchFieldException nsf) {
					log.error(nsf.getMessage());
					throw new JspException(nsf);
				}
			}
		} catch (IllegalAccessException iae) {
			log.error("Illegal Access Exception - maybe a classloader issue?");
			throw new JspException(iae);
		}

		// Continue processing this page
		return (SKIP_BODY);
	}

	public String getClassName() {
		return this.clazz;
	}

	public String getScope() {
		return (this.scope);
	}

	/**
	 * Converts the scope name into its corresponding PageContext constant
	 * value.
	 * 
	 * @param scopeName
	 *            Can be "page", "request", "session", or "application" in any
	 *            case.
	 * @return The constant representing the scope (ie.
	 *         PageContext.REQUEST_SCOPE).
	 * @throws JspException
	 *             if the scopeName is not a valid name.
	 */
	public int getScope(String scopeName) throws JspException {
		Integer scope = (Integer) scopes.get(scopeName.toLowerCase());

		if (scope == null) {
			throw new JspException("Scope '" + scopeName
					+ "' not a valid option");
		}

		return scope.intValue();
	}

	public String getVar() {
		return (this.var);
	}

	/**
	 * Release all allocated resources.
	 */
	public void release() {
		super.release();
		clazz = null;
		scope = Constants.class.getName();
	}

	// ~========== From Struts' TagUtils class =====================

	/**
	 * @jsp.attribute
	 */
	public void setClassName(String clazz) {
		this.clazz = clazz;
	}

	/**
	 * @jsp.attribute
	 */
	public void setScope(String scope) {
		this.scope = scope;
	}

	/**
	 * @jsp.attribute
	 */
	public void setVar(String var) {
		this.var = var;
	}
}
